Implement correct OS and CC detection.

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index 8b27c19a65f45d92cb8fdf2f52f0adad14715865..571b1e2ee18ea4f98504926ec0d0ed1b751fb8a5 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -44,6 +44,8 @@
 #ifndef V8_PLATFORM_H_
 #define V8_PLATFORM_H_
 
+#include <stdarg.h>
+
 #ifdef __sun
 # ifndef signbit
 namespace std {
@@ -52,16 +54,6 @@ int signbit(double x);
 # endif
 #endif
 
-// GCC specific stuff
-#ifdef __GNUC__
-
-// Needed for va_list on at least MinGW and Android.
-#include <stdarg.h>
-
-#define __GNUC_VERSION__ (__GNUC__ * 10000 + __GNUC_MINOR__ * 100)
-
-#endif  // __GNUC__
-
 
 // Windows specific stuff.
 #ifdef WIN32
@@ -132,7 +124,7 @@ class Socket;
 
 #ifndef V8_NO_FAST_TLS
 
-#if defined(_MSC_VER) && V8_HOST_ARCH_IA32
+#if V8_CC_MSVC && V8_HOST_ARCH_IA32
 
 #define V8_FAST_TLS_SUPPORTED 1
 
@@ -154,7 +146,7 @@ inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
                                       kPointerSize * (index - kMaxInlineSlots));
 }
 
-#elif defined(__APPLE__) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
+#elif V8_OS_DARWIN && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
 
 #define V8_FAST_TLS_SUPPORTED 1
 
@@ -385,7 +377,7 @@ class OS {
   // the platform doesn't care. Guaranteed to be a power of two.
   static int ActivationFrameAlignment();
 
-#if defined(V8_TARGET_ARCH_IA32)
+#if V8_TARGET_ARCH_IA32
   // Limit below which the extra overhead of the MemCopy function is likely
   // to outweigh the benefits of faster copying.
   static const int kMinComplexMemCopy = 64;
@@ -399,7 +391,7 @@ class OS {
   static void MemCopy(void* dest, const void* src, size_t size) {
     MemMove(dest, src, size);
   }
-#elif defined(V8_HOST_ARCH_ARM)
+#elif V8_HOST_ARCH_ARM
   typedef void (*MemCopyUint8Function)(uint8_t* dest,
                                        const uint8_t* src,
                                        size_t size);